A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the U.S. Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.
1. Field of the Invention
The present invention relates generally to a position indicating device for use with an information processing system such as a computer and, more particularly, to a position indicating device for use with an information processing system operating in harsh environmental conditions.
2. Description of Prior Art
It is well known for an information processing system such as, for example, a computer, to use one or more input devices such as, for example, a keyboard and a position indicating device. As referred to herein a position indicating device is a device operated by a user of the information processing system to identify a position of a cursor on a display device (e.g., a screen of a display monitor). The cursor is repositioned on the screen in relation to a distance and direction of movement of the position indicating device. Examples of such position indicating devices include a mouse, a pressure sensitive pad, a joy stick, a light pen, a roller ball or trackball, a slide-roller, and the like.
Position indicating devices typically include sensors and electronic circuits for translating linear motion of the devices (e.g., X-axis and Y-axis components of motion) into signals that are passed to the information processing system to change the position of the cursor on the screen. A perceived drawback of conventional position indicating devices is that accurate translation of the linear motion suffers when contaminants such as, for example, dirt, dust or liquids are present within the environment in which the information processing system is operating.
Efforts have been made to limit and/or eliminate adverse effects of such environmental contaminants. For example, U.S. Pat. No. 5,583,541, issued Dec. 10, 1996, to Erik Solhjell, discloses a mouse or track ball having a roller ball mounted within a housing and three free rollers in contact with an outer peripheral surface of the roller ball. A core of the roller ball includes a magnetic material. A pair of Hall effect sensors detect a changing magnetic force emitted from the core as the roller ball rotates. A comparator outputs a digital waveform corresponding to the changing magnetic force and representing the movement of the roller ball. Solhjell describes that the mouse can tolerate a certain amount of dust before experiencing translation problems due to resulting contamination of the roller ball. The disclosure of this U.S. patent is incorporated by reference herein in its entirety.
Similarly, Japanese patent document number JP 240716 A, published Sep. 25, 1990, discloses a track ball device having multipolar magnets attached at ends of rotary shafts. Hall elements located in proximity to the magnets detect magnetic flux changes as the magnets rotate by the Hall elements. The magnetic flux changes, in effect, produce a Sine curve representing track ball movement. These patent documents are seen to disclose conventional trackball and mouse devices that sense ball position magnetically to minimize an adverse impact on mechanical and optical sensing components caused by environmental conditions such as dust and dirt.
U.S. Pat. No. 5,214,415, issued May 25, 1993, to Richard Pandolei, discloses an electromagnetically shielded cursor control assembly. The assembly includes a pliable plastic seal to keep environmental contaminants such as dirt and water out of a housing having electrical components (e.g., ball motion sensors) and mechanical components (e.g., an electrically conductive rollerball) of the assembly stored therein. The disclosure of this U.S. patent is incorporated by reference herein in its entirety. German patent document number DE 197 36 928 C1, published Apr. 8, 1999, discloses a cordless mouse having a movement sensor, a processor and a transducer located within a hermetically sealed and sterilized housing. These patent documents are seen to describe sealing all mechanical and electrical components of the trackball devices in housings to minimize, or substantially eliminate contaminates entering the housing.
The inventor has realized a number of deficiencies in these techniques for attempting to protect a mouse or trackball device from harsh environmental conditions. For example, despite best efforts to maintain such conventional systems dust, dirt and other contaminates eventually invade the housing and/or compartment containing the mechanical and electrical components of the mouse.
Accordingly, a need exists for a position indicating device that reliably minimizes the effects of contamination of components of the position indicating device and for a device that can be decontaminated for continued dependable performance in harsh environmental conditions. One solution is proposed in commonly owned U.S. Pat. No. 5,850,142, issued Dec. 15, 1998, to Chris P. Rountos and Richard M. Passaro, which describes a magnetically actuated control device (e.g., joystick) for use in harsh environments. The disclosure of this U.S. patent is incorporated by reference herein in its entirety.
Accordingly, it is an object of the present invention to provide an improved position indicating device for use with an information processing system operating in harsh environmental conditions.
It is another object of the present invention to provide a position indicating device having mechanical components located within an opened compartment and electronic components located within a sealed compartment such that the electronic components are free of contamination from harsh environmental conditions while mechanical components, which may be exposed to contamination, can be readily removed from the opened compartment, decontaminated and returned to the opened compartment for continued operation of the position indicating device.
Further objects of this invention will become more apparent from a consideration of the drawings and ensuing description.
The above and other objects are achieved by an improved position indicating device. The position indicating device includes a housing having a sealed compartment and an opened compartment. A trackball is located in the opened compartment. A plurality of drive tube assemblies are also located in the opened compartment for supporting a periphery of the trackball. In one embodiment, the plurality of drive tubes include an X-axis drive tube and a Y-axis drive tube. The X-axis drive tube and the Y-axis drive tube each have a sealed magnet assembly affixed thereto. The drive tube assemblies and sealed magnetic assemblies generate a north-to-south pole magnetic field angle as the drive tube rotate. The sealed compartment includes an X-axis angle sensor, an X-axis signal conditioner, a Y-axis magnetic angle sensor, and a Y-axis signal conditioner. The angle sensors and signal conditioners sense and measure the north-to-south pole magnetic field angle generated by the rotating drive assemblies and sealed magnetic assemblies. The sealed compartment also includes a processor. The processor is coupled to the angle sensors and the signal conditioners and determines a change in consecutive magnetic field angles. The processor translates the change into an indication of linear motion of the position indicating device. The processor formats the indication into a signal, which it then transmits to a host device such as an information processing device.
In one embodiment, the trackball and the plurality of drive tube assemblies are components of a sub-chassis assembly that is installed in the opened compartment. In one embodiment, the position indicating device includes a cover removably mounted over and enclosing the opened compartment. When the cover is removed the sub-chassis assembly is removable from the opened compartment.